One Stroke Puzzle

Draw every line in one stroke without lifting your pen — 120 free levels plus “Can it be drawn?” bonus puzzles

👥 1 player🎲 Board & Puzzle⚡ No download · No sign-up

🕹️ How to play

How to start a one stroke puzzle: Press any dot to start — there is no start button. Drag toward a dot connected to it; entering that dot's circle completes the line, which turns solid gold, and the “Lines 1/6” counter goes up.
How to draw the lines: Always continue from the glowing pen head to a dot joined by a line you have not drawn yet. You may pass through a dot as often as you like, but each line only once. Where two lines cross there is no dot, so you cannot turn there.
What happens if you lift your finger: Nothing is lost: lifting just pauses. Press the glowing pen head to keep drawing, or tap a dot connected to it to draw one line at a time.
How to undo a wrong line: Tap Undo to take back the last line, all the way back to before your first press; dragging back along the line you just drew does the same. Restart clears the board and the timer keeps running.
How a level is cleared: When every line is gold the drawing lights up in the order you drew it, and the result card shows stars, time and whether you made it in one clean stroke. Go to the next level or draw it again for a better time.

📖 Rules & variants

One stroke rules: start on any dot and travel along the lines from dot to neighbouring dot, covering every line exactly once. Dots can be revisited, lines cannot, and crossings are not dots. There is no losing — a dead end is always recoverable.

Where to start: count the lines at each dot. A dot with an odd number of lines is an odd vertex. With no odd vertices you can start anywhere and you will finish where you began; with exactly two you must start at one of them and finish at the other; with four or more the drawing is impossible.

Stuck at a dead end: when the pen head has no undrawn line left but lines remain, the leftover lines flash. Undo back to the last dot where you had a choice and take another line, or restart. Getting stuck costs no stars, only the one-stroke badge.

Free hints in three levels, no ads: the first lights up a dot you can start from or the next safe line, the second shows a few more lines, the third plays the solution. If your current path can no longer be finished, the hint says how many steps to undo and offers a one-tap “Undo k steps”.

Stars: clear without hints for 3 stars, with a first-level hint for 2, with a second-level hint or the demo for 1. Clear without undoing, restarting or getting stuck to earn the One Stroke badge. Each level keeps your best stars and fastest time.

Levels: 120 main levels in five chapters grow from 5 to 32 lines, and every level is unlocked from the start. The 12 bonus “Can it be drawn?” puzzles ask you to either draw it or press “Impossible” — the last one is the Seven Bridges of Königsberg. Random boards come in easy, medium and hard, each with a shareable code.

❓ FAQ

Where do you start a one line drawing puzzle?

Start at a dot with an odd number of lines if the drawing has two of them; if every dot has an even number, any dot works. Starting anywhere else on a drawing with odd dots always leaves lines you can't reach.

How can you tell if a shape can be drawn in one stroke?

A shape can be drawn in one stroke only if it is connected and has zero or two odd vertices. Four or more odd vertices make it impossible — this is Euler's result from the Seven Bridges problem, and the count of odd vertices is always even.

Can you go over the same line twice in a one stroke puzzle?

No — each line must be drawn exactly once, but you can pass through the same dot as many times as you need. Level 1 here is a bow tie that forces you through the middle dot twice.

Why can't the Seven Bridges of Königsberg be solved?

All four land masses touch an odd number of bridges, which gives four odd vertices. A one stroke path allows at most two odd points, its start and its end, so no route crosses all seven bridges once. Try it yourself in bonus level 12.

What is the trick to solving one line puzzles?

Start at an odd dot and save any line that would cut the remaining drawing in two for last. Finish small inner loops before leaving them, and when stuck, undo to the most recent fork instead of restarting.

What is the difference between an Euler path and an Euler circuit puzzle?

An Euler path covers every line once and may end elsewhere; an Euler circuit also returns to the start. Drawings with no odd vertices give circuits, drawings with exactly two odd vertices give paths from one odd dot to the other.

⚠️ All levels are original drawings. Records stay in your browser only and do not sync between devices. For fun only.

Last updated: 2026-10-19 · Saved on this device only